Differential scanning dilatometry, supplemented by differential scanning calorimetry, will be performed on lipid bilayer systems to investigate phase transition properties and elucidate molecular interactions. Studies will begin on phosphatidyserine bilayers to further our knowledge of head group interactions. Correlation of phase transition changes in frog nerve membranes with x-ray information will be attempted. The absolute specific heats of lipid bilayers in single phase regions will be determined and correlated with our previous determinations of the coefficient of thermal expansion. Measurements will be made on newly available super pure lecithin.